In-Depth

Serialize Arrays and ArrayLists to XML

The XmlSerializer class provides a great way to convert objects to XML and back. However, it can be difficult to serialize collections such as Arrays and ArrayLists properly unless you know a few tricks.

Technology Toolbox: XML

The XmlSerializer class provides a great way to convert (serialize) objects to XML and back (deserialize). However, it can be difficult to serialize collections such as Arrays and ArrayLists properly unless you know a few tricks.

This sample application demonstrates how you can add multiple Car class instances into an Array as well as an ArrayList, then serialize them into an XML structure. You can accomplish this serialization process by using special XML serialization attributes such as XmlArray and XmlArrayItem, found in the System.Xml.Serialization namespace. For example, this code demonstrates how you can identify the type within an ArrayList using the XmlArrayItem attribute along with the C# typeof keyword:

[XmlArray("carsArrayList")]
[XmlArrayItem("car",typeof(Car))]
public ArrayList CarsCollection {
   get {
      return _CarsList;
   }
   set {
      _CarsList = value;
   }
}

Here's the output generated by serializing the ArrayList:

<?xml version="1.0" encoding="utf-16"?>
<carsCollection xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <carsArrayList>
      <car>
         <license>1234</license>
         <color>Black</color>
      </car>
      <car>
         <license>4321</license>
         <color>Blue</color>
      </car>
   </carsArrayList>
</carsCollection>

Download the sample here. To view a live example, visit the XML for ASP.NET Developers Web site.

About the Author

Dan Wahlin (Microsoft MVP for ASP.NET and XML Web Services) is the founder of The Wahlin Group which specializes in .NET and SharePoint onsite, online and video training and consulting solutions. Dan also founded the XML for ASP.NET Developers Web site, which focuses on using ASP.NET, XML, AJAX, Silverlight and Web Services in Microsoft's .NET platform. He's also on the INETA Speaker's Bureau and speaks at conferences and user groups around the world. Dan has written several books on .NET including "Professional Silverlight 2 for ASP.NET Developers," "Professional ASP.NET 3.5 AJAX, ASP.NET 2.0 MVP Hacks and Tips," and "XML for ASP.NET Developers." Read Dan's blog here.

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